The most straightforward tests of hepatic involvement in the control of food intake come from experiments that infuse nutrients directly into the hepatic-portal (HP) vein. Previous studies have found that glucose infusions decrease, increase or have no effect on feeding. A systematic investigation of the conditions responsible for these different results has not been attempted. We have begun to investigate some of the parameters involved, and we propose here to continue this work. A parametric approach will be taken, consisting of three series of experiments. Each series will contain parallel behavioral experiments, with food intake and meal patterns as dependent variables, and metabolic experiments, which will examine the physiological effects of the infusions. The following issues are addressed: 1) The influence of the quantity of glucose infused into the HP vein in determining hepatic effects on feeding and metabolism. 2) The influence of HP glucose relative to other carbohydrates in determining hepatic effects on feeding and metabolism. 3) The influence of hepatic innervation in determining the ingestive and metabolic effects of HP nutrient infusions. This work is important because it will provide information about the hepatic mechanisms involved in feeding regulation and the conditions needed for their expression.